Relics: Radio communications: Global HF T-Index and Propagation

Global HF T-Index Map

"A map showing the difference between current observed hourly conditions and predicted monthly conditions for the global ionosphere. Depressions and enhancements are with respect to the Space Weather Services (SWS) predicted monthly T-Index for that month.

T-Index Predictions Table

"A table of observed and predicted values for the SWS T-Index. The T-Index is a measure of the behavior of the F-layer of the ionosphere and is used as an input for the SWS HF frequency prediction program ASAPS."

"The T-Index is calculated from the vertical MUF (foF2) obtained from SWS ionograms combined with the SWS world map grid point data. The grid point data form the SWS world maps of foF2, there are 576 maps, for two ionosheric levels (T=0, T=100), 12 months, and 24 hours.

An foF2 observation can be converted into a T-Index by interpolation/extrapolation of the line obtained from the maps at a geographic location i.e. two map T, foF2 value pairs and the observed foF2, then read off the corresponding T-value. The T-Index is predicted over a coming solar cycle to provide a long term ionospheric index trend for HF communicators." Source:Australian Government - Bureau of Meteorology, Space Weather Services